Only on 13, a former FBI Deputy Director talks about the elaborate set up behind the scenes and why a manhunt prompts extreme caution.

Imagine a bustling city on a typical weekday, all at once, on lockdown. That's what happened in Boston Friday morning.

A national counterterrorism expert says the "stay and shelter" order is the urban version of the search for the 1996 Atlanta Olympics bomber, Eric Robert Rudolph.

Terry Turchie is a Former FBI Deputy Assistant Director. By phone, he told 13 Investigates he's not surprised at how quickly the joint terrorism task force in Boston narrowed in on the suspects after observing them on surveillance at the crime scene.

"These are dangerous people and they're going to take every precaution and do everything they possibly can to keep the public safe while they are literally going door to door, business to business," Turchie said.

Turchie directed the task force that caught both Rudolph and the Unabomber Ted Kaczynski. He says 56 task force offices across the country, led by the FBI, have been working around the clock to provide support, intelligence and expertise to those on the front lines of the investigation.

Here in Indianapolis, that group is the Fusion Center.

Indiana Congressman Andre Carson was assigned to the unit prior to his appointment and subsequent election to serve in the House of Representatives in Washington.

"Numerous law enforcement agencies can bring different levels of expertise all in one place, from the FBI to State Excise Police, Excise Police, State Police, the U.S. Marshals and so on and so forth, where we can exchange information and help solve crimes more rapidly," explained Carson as he recalled his previous work.